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R Programming Articles
Page 76 of 174
How to find the variance of row elements of a matrix in R?
Finding the variance of columns is a common task in data analysis but often data is provided in wide format instead of long format, therefore, the cases are represented vertically and the variables are aligned horizontally and this data could be available in matrix or any other form. Therefore, the variance can be easily found by using apply function.ExampleM1
Read MoreHow to represent all values of X-axis or Y-axis on the graph in R using ggplot2 package?
If we have many unique elements or repeated in a column of an R data frame and create a graph using that column, either on X-axis or Y-axis then R automatically choses the axes labels, this might not display all the unique values of the column in the plot. Therefore, we can use scale_x_continuous function or scale_y_continuous function with labels depending on our requirement to display the column values.Consider the below data frame −Examplex
Read MoreHow to remove underscore from column names of an R data frame?
When we import data from outside sources then the header or column names might be imported with underscore separated values and this is also possible if the original data has the same format. Therefore, to make the headers shorter and look better we would prefer to remove the underscore sign and this can be easily done with the help of gsub function.Consider the below data frame −Examplex_1
Read MoreHow to replicate a matrix by rows in R?
The replication of matrix by rows means that repeating a matrix one or more times but row-wise. For example, if we have a matrix that contains only one row and three columns then the replication of that matrix three times will repeat that one row three times. This can be done by using rep function along with matrix function as shown in the below example.ExampleM
Read MoreHow to create a scatterplot using ggplot2 with different shape and color of points based on a variable in R?
In general, the default shape of points in a scatterplot is circular but it can be changed to other shapes using integers or sequence or the variable. We just need to use the argument shape inside geom_point function and pass the variable name. For example, if we want to create the scatterplot with varying shapes of a variable x then we can use geom_point(shape=x). And if we want to change the size then integer values can be used.ExampleConsider the below data frame −set.seed(151) x
Read MoreHow to subset factor columns in an R data frame?
Subsetting of factor columns can be done by creating an object of all columns using sapply with is.factor to extract only factor column in the future then passing that object into subsetting operator single square brackets. For example, if we have a data frame df that contains three columns x, y, z and two of them say x and y are factor columns then we can use Factors
Read MoreHow to create a data frame with a column having repeated values in R?
To create a data frame with a column having repeated values, we simply need to use rep function and we can repeat the values in a sequence of the values passed or repeating each value a particular number of times. For example, if we have three values 1, 2, 3 then the data frame can be created by repeating these values as 1, 2, 3, 1, 2, 3, 1, 2, 3, 1, 2, 3 or by repeating the same as 1, 1, 1, 2, 2, 2, 3, 3, 3.Example 1x
Read MoreHow to find the index of an element in a matrix column based on some condition in R?
We might want to find the position of a value in a matrix column which is less than a certain value. This will help us to identify the position of critical or threshold values in each column. For example, if we have a matrix M that contains 5 rows and 5 columns with vales in the range of 1 to 100 then we might want to find the index of values in each column that are less than 50 so that we can understand how many columns have such type of values. In R, we can easily do this by ...
Read MoreHow to remove the first replicate in a vector using another vector that contains similar elements in R?
To remove the first replicate in a vector using another vector, we can use match function. For example, if we have a vector x that contain values 0, 1, 2, 3, 4, 5 and 0, 1, 2 are repeated in another vector say then the removal of this replicate will result in values 3, 4, and 5. This can be done by using x[-match(y,x)].Examplex1
Read MoreHow to calculate root mean square error for linear model in R?
To find the root mean square error, we first need to find the residuals (which are also called error and we need to root mean square for these values) then root mean of these residuals needs to be calculated. Therefore, if we have a linear regression model object say M then the root mean square error can be found as sqrt(mean(M$residuals^2)).Examplex1
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